With the progress of the times and technologies, there is a soaring demand for mobility and information. More and more people wish to have high speed access to the Internet during movement, acquire urgent information and thereby complete desired matters. Thus, it is an inexorable trend to integrate mobility with the Internet.
For future wireless communication, air interface should be an Internet Protocol (IP)-oriented air interface, all services are transmitted over IP, and seamless roaming and handover between various heterogeneous networks is supported.
All the existing wireless communication standards give full considerations when handling IP-based data services. For instance, wideband code division multiple access (WCDMA) provides shared channel to enable data packets of multiple users to be shared-transmitted over one identical channel. Some emerging wireless communication standards, such as 802.11 and 802.16, which are worked out by the Institute of Electrical and Electronic Engineers (IEEE), are designed out of consideration for the characteristics of data communication at the very start.
In essence, however, all these existing standards merely map IP layer transmission to wireless transmission by adapting without integrating IP features with characters of a wireless system. This will undoubtedly weaken the overall performance of the system. For instance, the transmission control protocol (TCP), which is highly sensitive to end-to-end delay, reduces the size of transmission window in case of large delay and thus impairs throughput. In wireless communication, a relatively long coding block is employed in order to obtain a larger coding gain, and a comparatively long interleaving block is employed in order to effectively resist time-selective fade. However, long coding block and long interleaving block will increase delay of data packets and finally affect the overall performance of the system. Such an effect is especially conspicuous when data packets are small.
In general, the existing methods of handling IP-based data in a wireless communication system can be summarized as follows: upon arrival, data packets are formed into a physical layer data unit with a fixed size through segmenting or assembling, after coding, interleaving at the physical layer and being mapped to physical resources, the unit is emitted on the wireless channel. Since only data packets of one service of one user can be transmitted each time, if a data packet is very small, then it needs to be filled with bits or wait for subsequent data packets. This wastes resources or increases delay.